1. Field of the Invention
This invention relates to ball and socket joints such as are used in mechanical linkages, and is concerned with a construction of such a joint, as well as a method of assembling it together.
2. Description of the Prior Art
In mechanical engineering, rods or links having ball ends engaging in sockets in other components are used for transmitting forces and couples. There is a need for such a construction in a hydraulic pump of the variable delivery type, employing an oscillating barrel, such as that described in French Patent Application No. 78 16406 filed by the assignees of the present applicant on June 2, 1978 with the title "Multi-Cylinder Variable Delivery Hydraulic Pump/Motor".
In such machines the relative movements of the parts require that the joint should transmit both compressive and tensile forces, and also forces of varying direction, between a piston and a connecting rod and between the connecting rod and the driving or output shaft.
Hitherto such a ball and socket joint has been formed by:
(1) Inserting the spherical ball head into an appropriately shaped socket in the other component and then peening over or swaging in the mouth of the socket.
(2) Using a split socket made of two half-shells which are secured together around the ball head.
(3) Forming a hemispherical part-socket in the component, and clamping the ball head into it without any play by means of a counter-plate which also has formed in it a part-spherical socket, the part-spherical surfaces in the component and in the counter plate being guided to be accurately coaxial, or
(4) Forming a hemispherical part-socket in the component and completing the socket by a counterplate of which the alignment is achieved automatically. In this case the clearance or play between the ball head and the socket has to be controlled on assembly by the degree of deformation of the counter-plate, and this is a tricky operation to control accurately.
In the case of the multi-cylinder pump mentioned above, the control of the clearance is further complicated by the fact that several connecting rods have to be connected to a common component by the use of a single counter-plate, and in practice it is almost impossible, because of manufacturing tolerances, to obtain equal clearances in all the joints.